<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>aa</title>
</head>
<body>
document.domain 具有相同的一级域名
<iframe src="http://localhost:2000/c.html#iamfroma" frameborder="0" id="frame"></iframe>
<script>

</script>
</body>
</html>